DC motor rotation information detecting device

Abstract

A rotation information detection device detects rotation information of a DC motor based on a surge component waveform superimposed on a voltage waveform between the terminals of the DC motor or a current waveform of the DC motor, a circuit is provided which supplies a current of a current value I pwm 45% during motor forward rotation or I pwm 55% during reverse motor rotation to the motor over the period from when the motor starts braking operation to when it stops.

1. A DC motor rotation information detecting device for detecting rotation information, comprising:
 a detection circuit that detects a surge component waveform superimposed on a signal waveform of at least one of a current flowing through a DC brush motor and a voltage between the terminals of the motor; and 
 a control circuit that controls the current flowing through the motor in a period from when the motor starts braking operation to when the motor stops to be equal to or greater than a reference current value set as a lower limit, 
 wherein the control circuit controls the current by pulse width modulation. 
 
   
   
     2. The DC motor rotation information detecting device according to  claim 1 , wherein the reference current value is set in advance as a current value that enables appearance of the surge component waveform superimposed on the signal waveform. 
   
   
     3. The DC motor rotation information detecting device according to  claim 1 , wherein the reference current value is set so that torque added to the motor through the current is smaller than loss torque obtained by adding internal loss torque of the motor and external loss torque by an external load applied to the motor. 
   
   
     4. The DC motor rotation information detecting device according to  claim 1 , wherein the circuit supplies the current of the reference current value to the motor over the period from when the motor starts the braking operation to when the motor stops. 
   
   
     5. The DC motor rotation information detecting device according to  claim 4 , wherein a direction of the current is the same as that of an induction current fed by counter-electromotive force due to power generation operation during the braking operation of the motor. 
   
   
     6. The DC motor rotation information detecting device according to  claim 4 , wherein the current adds torque to the motor in a direction opposite to a direction of rotation due to inertia during the braking operation. 
   
   
     7. The DC motor rotation information detecting device according to  claim 1 , wherein the circuit for controlling the current includes a bridge circuit driven to perform current control by the pulse width modulation, and a voltage regulator that regulates a voltage applied to the bridge circuit to a constant voltage. 
   
   
     8. A DC motor rotation information detecting device for detecting rotation information, comprising:
 a detection circuit that detects a surge component waveform superimposed on a signal waveform of a voltage between the terminals of a DC brush motor; and 
 a control circuit that provides a section in which an impedance between the terminals of the motor is increased, as a detection region of the surge component waveform is superimposed on the signal waveform, 
 wherein the control circuit provides the section cyclically through control of a current flowing through the motor by pulse width modulation. 
 
   
   
     9. The DC motor rotation information detecting device according to  claim 8 , further comprising:
 a rotation signal extraction circuit that extracts the surge component waveform from the signal waveform. 
 
   
   
     10. The DC motor rotation information detecting device according to  claim 9 , further comprising:
 a rotation pulse generation circuit that generates a pulse signal by binarizing the surge component waveform extracted by the rotation signal extraction circuit based on a predetermined threshold value. 
 
   
   
     11. The DC motor rotation information detecting device according to  claim 10 , further comprising:
 a re-trigerrable one-shot circuit that forms a pulse signal corresponding to a pulse width set re-triggerable in advance, 
 wherein the pulse signal generated by the rotation pulse generation circuit is used as a trigger. 
 
   
   
     12. A DC motor rotation information detecting device for detecting rotation information, comprising:
 a detection circuit that detects a surge component waveform superimposed on a signal waveform of at least one of a current flowing through a DC brush motor and a voltage between the terminals of the motor; and 
 a control circuit that provides a section in which impedance between the terminals of the motor is increased as a detection region of the surge component waveform superimposed on the signal waveform; 
 a rotation signal extraction circuit that extracts the surge component waveform from the signal waveform; 
 a rotation pulse generation circuit that generates a pulse signal by binarizing the surge component waveform extracted by the rotation signal extraction circuit based on a predetermined threshold value: and 
 a re-triggerable one-shot circuit that forms a pulse signal corresponding to a pulse width set re-triggerable in advance, 
 wherein a pulse width set in the one-shot circuit is variable according to a rotation speed of the motor and 
 wherein the pulse signal generated by the rotation pulse generation circuit is used as a trigger. 
 
   
   
     13. The DC motor rotation information detecting device according to  claim 12 , wherein the threshold value is variable according to operation conditions of the motor. 
   
   
     14. The DC motor rotation information detecting device according to  claim 13 , wherein the operation conditions of the motor include at least one of an operation mode, a rotation direction and a rotation speed of the motor.